1. Field of the Invention
This invention relates to an improvement of a plate type membrane module.
2. Background of the Invention
A plate type membrane module is well known in the art which filters a solution by ultrafiltration or reverse osmotic filtration. The unfiltered solution will hereinafter be referred to as "raw solution" and the filtered solution as "permeation".
The fundamental structure of a plate type membrane module is as shown in FIG. 1. In the module, a number of units 1' are laminated with spaces therebetween which serve as raw solution passageways. Each of the units 1', as shown in FIG. 2, is made up of a membrane supporting plate 11' having permeation passage grooves 13' on both its sides. Membranes 12' are formed on both sides of the plate 11'. As shown in FIG. 1, the axial ends of the units 1' have raw solution passage holes a.sub.i ' and a.sub.o '.
Roughly stated, the device filters the raw solution as follows. While the raw solution is flowing as indicated by the arrow F', the solvent of the solution is separated from the raw solution or impurities as it passes through the membranes 12' of the units 1'. The liquid thus permeated is led out of the filter device through the permeation passage grooves 13' (means for leading the liquid out of the filter device is not shown in detail).
In this type of module, shown in FIG. 3, the units 1' employ corrugated plates 11" of plastics as film or membrane supporting plates on which membranes 12" are laid. In raw solution passageways 2" between the units, the membranes 12" are bent inwardly with the tops of the waveform of the corrugated plates 11" as fulcrums. The waveforms of the corrugated plates 11" on both sides of each raw solution passageway 2" are completely opposite in phase to each other. That is, each of the raw solution passageways 2" is made alternately narrow and broad. The speed of flow of the solution is increased at the narrow parts of the passageway and decreased at the broad parts so that the flow of the solution pulsates and the membranes are vibrated by the solution thus pulsated. Since the membranes are supported by a number of fulcrums, they may be readily fatigued or damaged at the fulcrums.